GMC 2008 Acadia - Manual (Page 359)

Headlamp Aiming
Headlamp aim has been preset at the factory and
should need no further adjustment.
However, if your vehicle is damaged in a crash, the
headlamp aim may be affected. Aim adjustment to the
low-beam headlamps may be necessary if oncoming
drivers flash their high-beam headlamps at you
(for vertical aim).
If the headlamps need to be re-aimed, it is
recommended that you take the vehicle to your
dealer/retailer for service.
Bulb Replacement
For the proper type of replacement bulbs, see
Replacement Bulbs on page 5-46.
For any bulb changing procedure not listed in this
section, contact your dealer/retailer.
Halogen Bulbs
{ CAUTION:
Halogen bulbs have pressurized gas inside
and can burst if you drop or scratch the bulb.
You or others could be injured. Be sure to read
and follow the instructions on the bulb
package.
5-45